Electromagnetic switch



Nov. 23, 1948. B. HlNKs Y ELECTROMAGNETIQ SWITCH Filed Oct. 19, v.194:3

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Patented Nov. 23, 1948 UNITED STATES PATENT OFFICE ELECTROMAGNETICSWITCH Bernardllinks, Willenhall, England Application October 19, 1943;Serial No. 506,892 In Great Britain October 20, 1942 (Cl. 20G-104) sfClaims'. 1

This. invention relates; to electro-magnetic motor starter switches.v ofthe type comprising an electro-magnet coi-l and a divided magnetic yokeone part of which carries contactsl which are moved against contacts onthe frameof the switch when the coil is energized, the said magneticyoke part also moving` against the other part of the magnetic yoke part,and` it has for its object to open the said magnetic. coil circuit orprevent the closing of the coil circuitl when the contacts are badlyworn and require,- renewing. Thus liability of endangering themotorcontrolledby theswitch by relying on overloads or the like is obviated.A further object is to. provide means' for indicating the state ofcorrosion of the'contacts without the need' for openingV the switch. Astillfurther object of the invention is to automatically compensate forthe reduction of pressureon thecontacts caused by erosion or wear andto. increase the life of the contacts. Another-object of the inventionis to prevent arcing and burning ot the contacts caused by bounce atmake and still' another object is to simplify and improve thereliability of the construction of the switch..

In the. drawings.:

Figure 1 isy a side elevation of one form of electro-magnetic switchconstructedaccording to this invention.

Figure 2 is an end'elevation.

Figure 3 illustrates a modified form of switch actuated from the yoke oftheelectro-magnet.

Figure 4 is`v a circuit diagram of the switch.

According to one form of the invention as shown by Figures 1 and 2, theelectro-magnet operating the contacts comprises a magnetic coil Bmounted on the insulating frame-22' andthe parts 35 and 32 of a dividedmagnetic yoke are-sl-idably mounted? in relationl to the coil B andyframe 22, the part 32V carrying'. the movable contacts'. Thecoil B is incircuit with an electric motor and the circuit is made by a pushbuttonswitch. When the circuit is made bythe. movable contact 3| bridging thefixed contacts 24, the openingv and closing of the circuit iscontrolledl by an auxiliary switch, the eiective operation of which iscontrolled' by.y the position of the complete magnetic yoke. A terminalstrip'l is mounted'on each side of an insulating frame`- member 22 andiis shaped to form a cylindrical rib 23 extending across the width of thestrip and' the iixed contact 24. is pivotallyI mounted onr thiscylindricalA rib 3' and comprises a metal strip which is curved: nearythe centre` to form a curved' socketl 25 for swivelling onthe.cylindrical rib 23. Cine'le'nd` of the strip'extends from the socketinwardly to form a contact arm or'blade 24a, whilst the other endextends up- Wardly from the socket to form an arm 26 for conneotion to ahelical spring 21. One end of the helical spring is fixed on aninsulating bush mounted on a pin 28 Xed to the terminal strip 21, whilstthe other end of the spring is mounted ona crossfpin 29 bridged across aslotted portion of the said upwardly directed arm of the fixed contactstrip. The helical spring 21 pulls the contact strip on to thecylindrical rib and normally swivels theV contact spring until theinturned end 26a of the said upwardly directed arm 26, forming a stop,moves against the terminal strip. The contact 3| for bridging tworesiliently supporting xed contacts 24 is mounted on themagnetc yokeportion 32 through the medium of. an insulating block 33 and the endportions or blades of thisV bridge Contact are curved. The bridgeContact 3.I is loosely fitted on the fixing pin so that it willautomatically adjust itself on the contacts 24. When the current ispassed through the coils B of the electro-magnet, the yoke portion 32 ispulled upwardly and the bridge contact 3l. strikes the contact. arms 24aof the Xed contacts 24 andV such arms are pivoted upwardlyicy-'swivellingf the contacts on the cylindrical ribs-23. The initialturning movement of each xed Contact stretches the helical' spring 2land the spring is" so arranged that as the angular'movement increases sothe rate of extension of the springr increases to a greaterv extent,that is to say', the spring resistanceI to movement increases at agreater rate than the angular movement. The upper portion of themagnetic yoke 35 is held in an outwardv position' by a spring or thelike, so` that when the magnetic coil is energised the yoke portion 35is pulled in.- wardly againstL the force of the spring. For this purposethe'- magnetic yoke 35 is secured' to4 the spindle or slide 36. slidablymounted in the U- sliaped frame 3T fixed to the frame of the switch. Thespindle 35. has a spiral spring 38 thereon which bears against a head onthe spindle and' against the' frame 3'! to normally urge the spindleoutwardly. The innerend of the spindle has a head with a rectangularopening 39 therein and the yoke 35 is secured to the frame 39a by meansof a U-shaped piece' 40' engaging in the opening 39 so-that the yoke 35is capable of upward move-V ment onl the part 39a. The upper yokeportion 35- netically attracted to the upper portion and the twocontact, therupper portion is ffree to move upwardly, the upper portionis raised until the springsy actingV on the pivotedy fixed contacts 2li`resist the upward moverent when the parts will come to rest in aposition balanced by the said springs 2l. When the magnetic coil isenergised the upper yoke 35 is also attracted downwardly towards thelower yoke portion 32 against the tension of the spring 38 and when theyoke portions contact, the complete yoke is brought to rest bythe pullof the spring 38 in one direction. and the 'pull of the springs 2l inthe opposite direction. The downward or inward movement oi the yoke 35is utilised to close an auxiliary switch. For this purpose a lever 4| ispivoted on the tting 42 xed to the frame 31 and this lever is connectedto the spindle 36 so that the upward and downward movement of thespindle pivots the lever 4l upwardly and downwardly. A bar 43 ispivotally connected to the end of the lever 4l and such bar carries abridge contact 44 which is slidably mounted on the bar 43 against thepressure of the spring 45. The fixe-d contacts 46 of the auxiliaryswitch are mounted on an insulating bracket 41 fixed to the frame of themain switch and the bar 43 is slidably guided in a slot through thebracket 4l. l/Vhen the electro-magnet is energised and the yoke 35 ismoved downwardly, the auxiliary switch is closed to maintain theenergising current through the electro-magnetic coil. Should the contactarm 24a and a bridge contact 3| become worn by corrosion, the thicknesswill be reduced and consequently the lower yoke 32 would have to beraised a 4higher distance to place the same tension on the springs 2lias when the contacts are not worn and the full thickness. The tension ofthe springs 21 being balanced by the tension of the spring 38, if a lesstension is placed on the springs 21 less tension will also be placed onthe spring 38 and the contacting yoke parts 35 and 32 will be brought torest at a higher level and consequently the downward movement of theyoke 35 will be less and the pivotal movement of the lever 4I will alsobe less. When the contact 24a and 3l have been reduced to apredetermined thickness by corrosion, the movement of the bar 43 willnot be suilicient to close the auxiliary switch. The spring 2l is placedin tension when the blade of the movable contact bears on the blade 24aof the xed Contact which tension reacts against the magnetic forcecontrolling the position of the complete magnetic yoke 35-32 and theblades are so arranged that the place of contact is positioned inrelation to the yoke so that any reduction in thickness taken from thecontacting surfaces alters such relative position and consequently thepressure of the spring 2l. The magnetic yoke therefore comes to rest ata new position with the springs 21 and 38 balanced.

The arm 4| passes through a slot in the frame member 31 and a scale 31ais marked at the side of the slot to indicate the condition of thecontacts. The bottom marking will indicate the position when thecontacts are not worn and the top marking will indicate when thecontacts are in an un-safe condition. Intermediate markings will alsoindicate the state of wear or thickness of the contacts. Therefore thecondition of the contacts can be noted at any time from the outside ofthe switch. In some instances the auxiliary switch operating asdescribed cannot be used, such as for instance when a iioat controls aswitch for electric motors driving pump sets. In such case an auxiliaryswitch is used which normally opens and when the contacts have becomeworn to a dangerous condition, the auxiliary switch is closed. As shownby Figure 3, a convenient form of switch is similar to the aux- 4 iliaryswitch aforedescribed, but with its position reversed, that is to say,the bridge contact 48 closes on the iixed contacts 49 on thev upwardmovement of the bar 43 which is arranged similarly as the bar 43 ofFigure 2. When the auxiliary switch is closed, a secondary circuitincluding a secondary coil wound on the electromagnet is closed andheats a bimetal strip 30 and after the time delay during the heating ofthe metal strip, such strip opens the magnet coil circuit and so opensthe main switch. Standard overloads as now used on existing switches canbe used in lieu of the thermal trip as shown.

Fixed contacts hereinbefore referred to, contacts mounted on astationary part of switch.

The curved ends of the bridge contact wipe over the blades 24a, and willco-me to rest at a place beyond the place of any initial arcing.

Figures 1 and 2 show the auxiliary switch in theform of a retainingswitch and the bi-metal switch 3U is not in action. When the arrangementof the switch as shown by Figure 3 is used, the bi-metal switch `comesinto action; this is shown by the diagram, Figure 4, which shows in fulllines the circuit when the auxiliary switch is used as a retainingswitch, that is to say, when the press button switch is closed, theretaining switch maintains the electro-magnet coil circuit closed andthe release of the press button does not open the coil circuit, thedotted lines showing the circuit when the bi-metal switch 3i! is used.

I claim:

l. An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil on the frame andenergised from the electric supply line voltage, a twin divided magneticyoke comprising a moving yoke portion with blade contacts connectedtherewith and with the contact surfaces substantially at right angles tothe axis of the magnetic coil, and a second moving yoke portion whichyoke portions are attracted into contact to form a complete yoke, fixedblade contacts and a spring device adapted to resiliently press thefixed blade contacts on the moving contacts when the switch is switchedon and form a balancing resistance to the movement of the yoke with theblade contacts thereon inwardly of the coil, a spring device exerting aforce on the said second magnetic yoke portion in the reverse directionto the magnetic forceso that the complete yoke is oatingly supported ina balanced position between the opposing spring pressure of the saidspring devices, and a second switch having a moving contact operated bythe movement of the magnetic yoke comprising an auxiliary switch havingfixed and moving contacts and mechanical means actuating the movement ofthe moving contact of the auxiliary switch by a multiplied movement ofthe said second yoke portion and for setting the position of the aux--.iliary switch moving contact according to the balanced position of the'complete magnetic yoke.

2. An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil on the frame, atwin divided magnetic yoke having a moving yoke portion with bladecontacts connected therewith and with the contact surfaces substantiallyat right angles to the axis of the magnetic coil and a second movingyoke portion which yoke portions are ladapted to be attracted intocontact, fixed blade contacts, a spring device are the :Masami adapted'to` resiliently press the xed blade contacts on the moving contacts whenthe switch i's switched on, andl form a: balancing resistance tothemovement of the yoke with the blade contacts thereon inwardly of thecoil, a spring device exerting a force on the said second magnetic yokeportion inthe reverse direction to the magnetic force so that thecomplete yoke is oatingly supported in a balanced position between theopposing spring pressure of the said spring devices and a second switchhaving a moving contact operated by the movement of the magnetic yokeand set with the main switch switched on at` a, position according, tothe balanced position of the complete yoke,v comprising an; auxiliaryswitch having. a, xed and a moving. contact, and mechanical means; for'actuating the moving contact oi the auxiliary switch` operated by themovement of the said second yoke portion and to multiply the movement ofthe latterl contact in relation to the movement of the yoke portion,comprising a lever pivoted to the switch frame and connected to thesecond yoke portiony a bar pivotally connected to said lever and movablymounted in relation to xed contacts of the auxiliary switch and a springpressed contact slidably mounted on said bar for engaging the lastmentioned fixed contacts.

3. -An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil, having a movingyoke portion with blade contacts connected therewith and with thecontact surfaces substantially at right angles to the axis of themagnetic coil and a second moving yoke portion which yoke portions areattracted towards one another into contact when the coil is energised,fixed blade contacts, a spring device adapted to resiliently press thefixed blade contacts on the moving contacts and form a balancingresistance to the movement of the yoke with the blade contacts thereoninwardly of the coil, a spring device exe-rting a force on the secondmagnetic yoke portion in the reverse direction to the magnetic force sothat the complete yoke is floatingly supported in a balanced positionbetween the opposing spring pressures of the said spring devices whenthe switch is switched on and a second switch having a moving contactoperated by the movement of the magnetic yoke and set with the mainswitch switched on at a position according to the position of thecomplete magnetic yoke comprising an auxiliary switch having fixed andmoving contacts, and mechanical means for actuating the moving contactof the auxiliary switch operated by the movement of the said second yokeportion and to multiply the movement of the second yoke portion,comprising a lever pivoted to a stationary part of the switch frame andpivoted to open or close the auxiliary switch, a member moved inwardlyby the inward movement of the second magnetic yoke portion and connectedto said lever and a scale over which the lever moves.

4. An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil on the frame, atwin divided magnetic yoke having a moving yoke portion with bladecontacts connected therewith and with the contact surfaces substantiallyat right angles to the axis of the magnetic coil, and a second movingyoke portion which yoke portions are adapted to be attracted intocontact when the magnetic coil is energised, xed blade contactsresiliently mounted on the frame of the switch 63 andeach comprising ahaving a vsocket portion between the arms, terminal' strips on the frameof the switch having a rib on which the said socket portion is pivotallymounted, a helical spring connected to one arm` and holding the socketon the rib to form a wiping contact and holding the other arm of thecontact in position so that when the moving contact moves thereagainstthe spring is placed in tension to form a spring contact and a balancingresistance to the movement of the yoke portion inwardly of the coil andthe arrangement being such that as the angular movement increases so therate of' extension of the spring increases to a greater extent, that isto say, the spring resistance to movement increases at a greater ratethan the angular movement, and thus balance the eXtra power of theelectromagnet, a spring device exerting a force on the said second yokeportion. in the reverse direction to the magnetic force so that thecomplete yoke is floatingly supported in a balanced position and asecond switch having a moving contact operated bythe movement of themagnetic yoke comprising an auxiliary switch having a fixed and a movingcontacts and mechanical means actuating the movement of the movingcontact of the auxiliary switch by a multiplied movement of the saidsecond yoke portion and for setting the position of the auxiliary switchmoving contact eccording to the balanced position of the completemagnetic yoke.

5. An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil on the frame, atwin divided magnetic yoke portion having a moving yoke portion withblade contacts connected therewith and with the contact surfacessubstantially at right angles to the axis of the magnetic coil, and asecond moving yoke portion which yoke portions are adapted to beattracted into contact to form a complete yoke when the coil isenergised, fixed blade contacts resiliently mounted on the frame of theswitch and each comprising a double armed member having socket portionbetween the arms, terminal strip on the frame of the switch having a ribon which said socket portion is pivotally mounted, a helical springconnected to one arm holding the socket on the rib to form a wipingcontact and holding the other arm of the contact in position so thatwhen the moving contact moves thereagainst, the spring is placed intension to form a spring contact and a balancing resistance to themovement of the yoke portion inwardly or the coil, a slide mounted onthe frame oi the switch, a spring urging the slide outwardly and with itthe said second magnetic yoke portion and adapted to co-act with thesaid springs of the xed contacts to iloatingly support the complete yokea balanced position when the magnetic coil is energised, a bracket fixedto the said second yoke carrying portion and having a slot engaged bythe slide so that the spring applies a pull on the second yoke portionwhen the said coil is energised but permits movement of the yoke portionand the slide to absorb shock, and a second switch having a movingcontact operated by the movement of the magnetic yoke comprising anauxiliary switch having a xed and a moving contacts and mechanical meansactuating the movement of the moving contacts of the auxiliary switch bya multiplied movement of the said second yoke portion and for settingthe position of the auxiliary switch moving contact according to thedouble armed member balanced position of the complete magnetic yoke.

5. An electro-magnetic motor starter switch of the type set forthcomprising a switch frame, a stationary magnetic coil on the frame, atwin divided magnetic yoke having a moving yoke por tion with bladecontacts connected therewith and with the Contact surfaces substantiallyat right angles to the axis of the magnetic coil, and a second movingyoke portion which yoke portions are adapted to be attracted intocontact when the magnetic coil is energisecl, xed blade contactsresiliently mounted on the frame of the switch and each comprising adouble armed member having a socket portion between the arms, terminalstrips on the frame of the switch having a rib on which the said socketportion is pivotally mounted, a helical spring connected to one arm andholding the socket on the rib to form a wiping conta-ct and holding theother arm of the contact in position so that when the moving contactmoves thereagainst the spring is placed in tension to form a springcontact and a balancing resistance to the movement of the yoke portioninwardly of the coil and the arrangement being such that as the angularmovement in- 8, creases so the rate of extension of the spring increasesto a greater extent, that is to say7 the spring resistance to movementincreases at a greater rate than the angular movement, and thusbalancethe eXtra power of the electromagnet.

BERNARD HINKS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 592,443 Pruckner et al Oct. 26,1897 704,665 Richards July 15, 1902 863,185 Jefferies Aug. 13, 1907978,377 Humphrey Dec. 13, 1910 1,494,762 Trcemel May 20, 1924 1,522,546Richmond Jan. 13, 1925 1,764,819 Anderson June 17, 1930 1,782,916Campbell et al Nov. 25, 1930 1,816,429 Getchell July 28, 1931

